So let me tell u guys how far I am by now.

I have a data sample of 15 numbers. I have verified the mean, and computed the standard deviation. I have found the quartiles and inter quartile range.
I have made a botched attempt at a quantile plot using the formula xi=r/(n+1)
not sure if that is correct, but i just got the percentile rank, and plotted that against the data values.

Here's the trouble, I am supposed to see if a normal distribution model, with the same average, and same deviation, can be used to describe the data. It asks How do the quartiles of the normal probability compare with the quartiles of the data, expressed in the same units. I found that the quartile of the normal distribution model were quite off, because I had one outlier datum that seriously screws this problem up.

I am not sure if I calculated that right. I figured in a normal distribution model one just takes about .68 and -.68 from the mean(Q2) to find the other , so I just found the IQR = 1.34896 x Standard Distribution. Then I divided the IQR by 2, and found the distance from Q2 to Q1 and Q3. Does that work?
It all gets fuzzy from there, because next I am supposed to use the normal probability model to determine what fraction of samples are above a given datum. I just used the z equation to find that. I feel like its wrong though.


Next I am supposed to construct a quantile-quantile plot for these data by comparing corresponding quantiles of a normal distribution with each datum?

I have seen a Q-Q graph, but I am still confused from the wording as to what goes on the axis's. any suggestions?

I am just struggling with my teachers venacular, and I really need help understanding z values.

Thanks for any advice, Great website!